Burling graphs, chromatic number, and orthogonal tree-decompositions

A classic result of Asplund and Gr\"unbaum states that intersection graphs of axis-aligned rectangles in the plane are $\chi$-bounded. This theorem can be equivalently stated in terms of path-decompositions as follows: There exists a function $f:\mathbb{N}\to\mathbb{N}$ such that every graph that has two path-decompositions such that each bag of the first decomposition intersects each bag of the second in at most $k$ vertices has chromatic number at most $f(k)$. Recently, Dujmovi\'c, Joret, Morin, Norin, and Wood asked whether this remains true more generally for two tree-decompositions. In this note we provide a negative answer: There are graphs with arbitrarily large chromatic number for which one can find two tree-decompositions such that each bag of the first decomposition intersects each bag of the second in at most two vertices. Furthermore, this remains true even if one of the two decompositions is restricted to be a path-decomposition. This is shown using a construction of triangle-free graphs with unbounded chromatic number due to Burling, which we believe should be more widely known.Comment: v3: minor changes made following comments by the referees, v2: minor edit

On the dimension of posets with cover graphs of treewidth 22

In 1977, Trotter and Moore proved that a poset has dimension at most $3$ whenever its cover graph is a forest, or equivalently, has treewidth at most $1$. On the other hand, a well-known construction of Kelly shows that there are posets of arbitrarily large dimension whose cover graphs have treewidth $3$. In this paper we focus on the boundary case of treewidth $2$. It was recently shown that the dimension is bounded if the cover graph is outerplanar (Felsner, Trotter, and Wiechert) or if it has pathwidth $2$ (Bir\'o, Keller, and Young). This can be interpreted as evidence that the dimension should be bounded more generally when the cover graph has treewidth $2$. We show that it is indeed the case: Every such poset has dimension at most $1276$.Comment: v4: minor changes made following helpful comments by the referee

Improved quality of life in patients with refractory or recidivant ascites after insertion of transjugular intrahepatic portosystemic shunts

Background. We have recently shown that the transjugular intrahepatic portosystemic shunt (TIPS) is more effective than paracentesis in the treatment of cirrhotic patients with severe ascites and can prolong survival in selected patients. Although an improved quality of life (QOL) has been suggested in these patients after the TIPS procedure, so far there are no data available to substantiate this assumption. Therefore, the aim of this study was to determine the effect of TIPS on the QOL in cirrhotic patients with refractory or recidivant ascites. Methods: 21 cirrhotic patients who underwent TIPS for refractory or recidivant ascites were investigated. All patients were pretreated with repeated paracentesis for at least 1 year. Before the procedure and at 3 and 6 months during follow-up, the patients themselves rated QOL, fatigue and physical performance on a visual analogue scale (range 0-100). Furthermore, QOL was determined by the QOL index (range 0-10) according to Spitzer. Results: Patients' rating of the QOL on the visual analogue scale significantly increased from 35 +/- 25 (baseline) to 64 +/- 28 (3 months), and 66 +/- 24 (6 months; p = 0.02). Similarly, the QOL index significantly increased from 6.9 +/- 2.0 (baseline) to 8.3 +/- 2.1 (3 months), and 8.6 +/- 1.7 (6 months; p < 0.001). The increase of QOL was more pronounced in patients with complete response to TIPS. Conclusions: We demonstrate that TIPS for refractory or recidivant ascites improves the QOL in patients with cirrhosis. Our data indicates that this improvement is dependent on the response to therapy. Copyright (C) 2002 S. Karger AG, Basel

The Effect of Smart Contracts on Online Investment Decisions: An Experimental Study in ICOs

The imbalance of internal and external knowledge for investments in Initial Coin Offerings (ICO) leads to an information asymmetry, where issuers may further exploit a moral hazard as a resulting mismatch of time and interest during lock-up situations. The existing regulatory vacuum is mirrored by literature, as scholars deliver insights on effective means of signaling. However, research on smart contracts as immutable mechanisms and effective signals to mitigate risks for online investments remains an untapped subject, whilst market demand for solutions to an existing agency problem remains high. To respond to a pressing research question, this study conducted a randomized between-subjects online experiment with a sample of 391 participants. Results include a significant positive effect of the implementation of smart contracts on investor decisions in a present lock-up situation

Emergent electric field control of phase transformation in oxide superlattices.

Electric fields can transform materials with respect to their structure and properties, enabling various applications ranging from batteries to spintronics. Recently electrolytic gating, which can generate large electric fields and voltage-driven ion transfer, has been identified as a powerful means to achieve electric-field-controlled phase transformations. The class of transition metal oxides provide many potential candidates that present a strong response under electrolytic gating. However, very few show a reversible structural transformation at room-temperature. Here, we report the realization of a digitally synthesized transition metal oxide that shows a reversible, electric-field-controlled transformation between distinct crystalline phases at room-temperature. In superlattices comprised of alternating one-unit-cell of SrIrO3 and La0.2Sr0.8MnO3, we find a reversible phase transformation with a 7% lattice change and dramatic modulation in chemical, electronic, magnetic and optical properties, mediated by the reversible transfer of oxygen and hydrogen ions. Strikingly, this phase transformation is absent in the constituent oxides, solid solutions and larger period superlattices. Our findings open up this class of materials for voltage-controlled functionality